Cosmetic composition with increased opacity

ABSTRACT

A cosmetic composition is disclosed comprising particle active and cosmetically acceptable carrier comprising hydrophobic material, wherein the hydrophobic material comprises less than 15% liquid oil by weight of the composition. The particle active comprises (i) water-insoluble shell component comprising inorganic material and having a refractive index of from 1.3 to 1.8; and (ii) core component comprising volatile liquid and having a refractive index of at least 1.2.

FIELD OF THE INVENTION

The present invention relates to cosmetic compositions. Moreparticularly, the present invention relates to such compositions fortopical application to skin wherein increased opacity is desired toprovide benefits such as masking blemishes, evening skin tone and/orskin lightening.

BACKGROUND OF THE INVENTION

Cosmetic compositions of various kinds are widely used by consumers.Skin care cosmetics such as moisturizing lotions or creams are appliedto obtain benefits of anti-aging, skin lightening and moisturizing,while make-up cosmetic products are applied to obtain desired optics andcolor benefits. Make-up cosmetics such as foundation and blemish-balmcreams are able to deliver such covering and color benefits as a resultof very high pigment and colorant content. Unfortunately, however, suchhigh loadings can lead to an undesired feature of poor tactile sensoryand for this reason moisturizers typically maintain low pigment dosage.It is the current trend that more and more make-up products are promotedto have moisturizer type in-use sensory and traditional moisturizers areformulated to deliver more perceivable optical benefits.

Whitening and opacifying optical properties delivered frommoisturizer-type products generally come from their intrinsic emulsionstructure (either W/O or O/W) and included particles with highrefractive index, such as micronized titanium dioxide and zinc oxide.When topically-applied such products are usually spread to a very thinfilm (typically ˜20 micron thickness) on the skin surface. This film issubject to a fast drying process during which emulsion droplets coalesceand break up and opacifying particles aggregate. As a consequence, thefilm loses most of its optical benefits within minutes afterapplication. Thus, in order to compensate the time-dependent loss ofoptical benefits, a high level addition of the opacifying particles maybe included in the formulation. However such heavy loadings typicallybring unnatural whiteness on initial application and are therefore notan ideal technical solution.

The present inventors have thus recognized that there remains a need toprovide cosmetic compositions that are capable of providing benefits,especially optical benefits, which are long lasting and/or actuallyincrease with time after application. The present inventors have foundthat such a need may be met by providing particle actives withparticular configuration and properties. In particular the inventorshave found that particles with a shell formed from inorganic materialhaving a specific refractive index and filled with a volatile materialhaving a specific refractive index can meet such a need.

The application of inorganic core-shell particles in cosmetics has beendescribed. In particular the use of such particles for encapsulatingactive materials has been described.

U.S. Pat. No. 7,758,888 (Sol-Gel Technologies Ltd.) discloses atherapeutic, cosmetic or cosmeceutic composition for topicalapplication, capable of stabilizing an active ingredient and deliveringthe active ingredient, comprising a plurality of microcapsules having acore-shell structure. The microcapsules have a diameter of approximately0.1 to 100 micron. The core of each microcapsule includes at least oneactive ingredient and is encapsulated within a microcapsular shell. Theshell is comprised of at least one inorganic polymer obtained by asol-gel process, and the shell protects the active ingredient beforetopical application and is designed to release the active ingredientfrom the microcapsules following application. The composition is said tobe useful in encapsulating active ingredients, such as benzoyl peroxide,that are unstable in other formulation, or are irritating to the skin.

WO 2011/076518 A (EVONIK DEGUSSA GMBH) discloses a powdery compositioncomprising: a) at least one powder in form of core-shell particles, thecore comprising liquid water or a liquid aqueous phase and the shellcomprising hydrophobic or phobized particles and b) at least one powdercomprising carrier and b1) at least partially water soluble liquidand/or b2) a water reactive substrate each located in and/or on thecarrier. Provision of such compositions in a powdery form allows theparticles to break upon application to the skin and so the particles arenot in the form of core-shell particles after application.

The foregoing publications do not recognize the utility of particleswith a shell having a certain refractive index and filled with avolatile material also having a certain refractive index in providingcosmetic compositions that are capable of providing optical benefits tothe skin, especially which benefits are long lasting and/or actuallyincrease with time after application. Furthermore the publications donot recognize the utility of applying such particles in cosmeticcompositions comprising hydrophobic material but with relatively lowcontents of liquid oil.

Definitions

Refractive Index

Refractive index values referred to herein are those determined at atemperature of 25° C. and a wavelength of 589 nm unless otherwisestated.

Particle Size

Where the size of particles is mentioned (other than “primary particlesize”) this means the number average diameter determined, for exampleusing scanning electron microscopy (SEM). Similarly “thickness” meansthe number average thickness determined, for example using scanningelectron microscopy (SEM). In a preferred method, cryo-SEM is used todetermine particle size and thickness. In cryo-SEM, a composition isquick-frozen in liquid nitrogen followed by cryo-planing to create aflat surface to be imaged. Typically the diameter and thickness are eachaveraged over at least 200 particles. For diameter determination, intactparticles are selected from the SEM image whilst for shell thickness,particles which have been sectioned are selected.

In the event that a particle is not spherical then “diameter” means thelargest distance measurable across the particle.

Where primary particle size is mentioned this means the size (diameter)measurable by transmission electron microscopy (TEM) using a method suchas that described by S. Gu et al in Journal of Colloid and InterfaceScience, 289 (2005) pp. 419-426.

Hydrophobic Material

By “hydrophobic material” is meant a substance that is attracted to andtends to dissolve in a non-polar solvent (such as n-octanol) inpreference to water at 25° C. and 1 atm. Preferred hydrophobic materialsare insoluble in water. The term “liquid oil” as used herein refers tohydrophobic material with a melting point below 25° C. at 1 atm.

“Non-liquid hydrophobic material” refers to hydrophobic material otherthan liquid oil. Preferred hydrophobic materials are non-volatile.

Solubility “Soluble” and “insoluble”, as used herein, refers to thesolubility of a substance in a solvent (which, unless otherwise statedis water). Soluble means a substance that dissolves in the solvent togive a solution with a concentration of at least 1 g per liter at roomtemperature (25° C.) and pressure (1 atm). Insoluble means a substancethat dissolves in the solvent to give a solution with a concentration ofless than 1 g per liter at room temperature and pressure.

Volatility

The term “volatile” as used herein refers to a substance which has avapour pressure of at least 1000 Pa at 25° C. and a non-volatilesubstance is one wherein the vapour pressure is less than 1000 Pa.

Leave-On and Wash-Off

The term “leave-on” as used with reference to compositions herein meansa composition that is applied to or rubbed on the skin, and leftthereon. The term “wash-off” as used with reference to compositionsherein means a skin cleanser that is applied to or rubbed on the skinand rinsed off substantially immediately subsequent to application.

Skin

The term “skin” as used herein includes the skin on the face (except eyelids and lips), neck, chest, abdomen, back, arms, hands, and legs.Preferably “skin” means skin on the face.

Miscellaneous

Except in the examples, or where otherwise explicitly indicated, allnumbers in this description indicating amounts of material or conditionsof reaction, physical properties of materials and/or use may optionallybe understood as modified by the word “about”.

All amounts are by weight of the final composition, unless otherwisespecified.

The term “solid” as used herein means that the material is not fluid at25 degrees C.

It should be noted that in specifying any range of values, anyparticular upper value can be associated with any particular lowervalue.

For the avoidance of doubt, the word “comprising” is intended to mean“including” but not necessarily “consisting of” or “composed of”. Inother words, the listed steps or options need not be exhaustive.

The disclosure of the invention as found herein is to be considered tocover all embodiments as found in the claims as being multiply dependentupon each other irrespective of the fact that claims may be foundwithout multiple dependency or redundancy.

Where a feature is disclosed with respect to a particular aspect of theinvention (for example a composition of the invention), such disclosureis also to be considered to apply to any other aspect of the invention(for example a method of the invention) mutatis mutandis.

SUMMARY OF THE INVENTION

In a first aspect, the present invention is directed to a cosmeticcomposition in the form of a paste, gel, liquid or monolithic solid andcomprising:

-   -   (a) particle active, wherein the particle active comprises:        -   (i) water-insoluble shell component comprising inorganic            material and having a refractive index (n_(s)) of from 1.3            to 1.8; and        -   (ii) core component comprising volatile liquid and having a            refractive index (n_(c)) of at least 1.2, wherein the core            component comprises at least 75% water by weight of the core            component; and    -   (b) cosmetically acceptable carrier comprising hydrophobic        material, wherein the hydrophobic material comprises less than        15% liquid oil by weight of the composition.

In a second aspect the invention is directed to a process for making anyembodiment of the composition of the first aspect, the processcomprising: combining the particle active with the carrier; andrecovering the composition.

In a third aspect the present invention provides a method for improvingone or more skin characteristics comprising the steps of:

-   -   I. providing a composition according to any embodiment of the        first aspect;        -   II. topically applying the composition to skin; and        -   III. allowing the volatile liquid to evaporate from the            particle active.

In a fourth aspect the invention provides use of a particle active forproviding a skin benefit selected from masking blemishes, evening skintone, skin lightening or a combination thereof, wherein the particleactive comprises:

-   -   (i) water-insoluble shell component comprising inorganic        material and having a refractive index (n_(s)) of from 1.3 to        1.8; and        -   (ii) core component comprising volatile liquid and having a            refractive index (n_(c)) of at least 1.2.

Preferably the particle active is as described in any embodiment of thefirst aspect of the invention.

In a fifth aspect the invention provides use of the composition of anyembodiment of the first aspect for providing a skin benefit selectedfrom masking blemishes, evening skin tone, skin lightening or acombination thereof.

All other aspects of the present invention will more readily becomeapparent upon considering the detailed description and examples whichfollow.

DETAILED DESCRIPTION

The only limitation with respect to the type of particle active that maybe used in this invention is that the same can be employed in a cosmeticcomposition suitable for topical application to skin, and that theparticle active comprises:

-   -   (i) water-insoluble shell component comprising inorganic        material and having a refractive index (n_(s)) of from 1.3 to        1.8; and    -   (ii) core component comprising volatile liquid and having a        refractive index (n_(c)) of at least 1.2.

Without wishing to be bound by theory, the present inventors believethat as the volatile liquid evaporates from the particle core (e.g.after application to skin), it is replaced by air. Air has a relativelylow refractive index and so a mismatch (or at least an increasedmismatch) in refractive index between the core and the shell of theparticle active develops. This in turn means that the light scatteringefficiency of the particles increases and the overall optical benefitsprovided by the composition evolve with time after application.

The shell component is water-insoluble but is preferably permeable towater. At least the shell should be permeable sufficient to allow thevolatile liquid to evaporate from the core when the particle active isexposed to air at 25° C. and 1 atm. Most preferably the shell componentis permeable sufficient to allow substantially all of the volatileliquid (e.g. 90-100% by weight of the total volatile liquid in the core)to evaporate from the core when the particle active is exposed to air at25° C. and 1 atm for 12 hours, or even 6 or 3 hours.

Typically the shell component will be solid.

The shell component comprises an inorganic material. A most preferredinorganic material for the shell component is inorganic polymer,especially inorganic polymer obtained by a sol-gel process as suchpolymers can be formed into shell-like particles using methods such asthose described for example in U.S. Pat. No. 7,758,888, the disclosureof which is hereby incorporated by reference in its entirety (butespecially column 13 [lines 15-39] thereof). Inorganic polymer ispreferably formed from pure silica, organically-modified silica, or acombination thereof, most preferably from silica.

The shell component may comprise organic material in addition toinorganic material but in a preferred embodiment the shell componentcomprises at least 80% inorganic material by weight of the shellcomponent, more preferably at least 90% and most preferably from 95 to100%. In an especially preferred embodiment the shell consists (or atleast consists essentially) of inorganic material, most especiallysilica.

The refractive index of the shell component should be sufficientlylarger than the refractive index of air such that once the volatileliquid evaporates from the core of the particle active, the air whichreplaces it has a significant refractive index mismatch with the shell.Thus the water-insoluble shell component has a refractive index (n_(s))of at least 1.3, more preferably at least 1.4. The refractive index isnot too high, however, otherwise the shell may have a significantrefractive index mismatch with the volatile liquid. Thus n_(s) is nogreater than 1.8, preferably less than 1.7, more preferably less than1.6 and most preferably less than 1.5.

The core component comprises volatile liquid and preferably consistsessentially of, or even consists of volatile liquid. The liquid isvolatile such that it may evaporate from the core when the particleactive is exposed to air at 25° C. and 1 atm. Preferably the volatileliquid has a vapour pressure of at least 2000 Pa at 25° C. mostpreferably at least 2.5 kPa. The liquid need not be too volatile,however, otherwise it may prematurely escape from the particle active.Preferably the volatile liquid has a vapour pressure of less than 50 kPaat 25° C. more preferably less than 15 kPa. Preferred volatile liquidsinclude volatile silicones, C1-C5 alcohols, water or a mixture thereof.Most preferred is water. Preferably the core component comprises atleast 50% water by weight of the core component, more preferably atleast 75%, more preferably still at least 85% and most preferably from90 to 100%.

The refractive index of the core component should be sufficiently largerthan the refractive index of air such that a refractive index mismatchdevelops or at least increases when the liquid is replaced by air. Thusthe core component has a refractive index (n_(c)) of at least 1.2, morepreferably at least 1.25 and most preferably at least 1.3. Therefractive index need not be too high and n_(c) may, for example, beless than 2.0, more preferably less than 1.8, more preferably still lessthan 1.5, even more preferably less than 1.45 and most preferably lessthan 1.4.

In a most preferred embodiment the refractive indices of the shell andcore are substantially matched such that a mismatch develops only whenthe volatile liquid evaporates from the core. For example, the ratio ofthe refractive index of the core to the refractive index of the shell(n_(c)/n_(s)) is preferably from 0.7 to 1.2, more preferably from 0.8 to1.1, most preferably from 0.85 to 1.0.

Light scattering properties of the particle active are enhanced if theparticles are micronized. Thus it is preferred that the particle activehas a particle size (D) of no greater than 50 microns, more preferablyless than 20 microns, more preferably still less than 10 microns, evenmore preferably less than 5 microns and most preferably less than 2microns.

It has been found, however that the particles need not be too small andeffective optical effects can be obtained with relatively largeparticles. Thus it is preferred that the particle active has a particlesize (D) of at least 200 nm, more preferably at least 500 nm, morepreferably still at least 600 nm, even more preferably at least 700 nmand most preferably at least 800 nm.

It has also been found that particle actives with relatively thickshells give especially good optical effects. Thus in a preferredembodiment the relationship between the thickness (L) of the shellcomponent and the size (D) of the particle active follows equation (I):

L·150 nm−0.25×D   (I).

The particle active is preferably spherical or spheroidal, mostpreferably spherical.

Preferably each particle of the particle active comprises (morepreferably consists essentially of or consists of) a single corecomponent encapsulated by the shell component.

The cosmetic composition preferably comprises the particle active inamount of from 0.001 to 20% shell component by weight of thecomposition, more preferably from 0.01 to 10%, more preferably stillfrom 0.1 to 6%, even more preferably from 0.2 to 4%, and most preferablyfrom 0.5 to 2.5%.

The composition of the present invention preferably comprises opacifyingparticles. These are particles with very high refractive index, i.e.,having a refractive index of at least 1.7. For example the opacifyingparticles may have a refractive index of greater than 1.8, morepreferably greater than 1.9 and most preferably from 2.0 to 2.7.Examples of such opacifying particles are those comprising bismuthoxy-chloride, boron nitride, titanium dioxide, zirconium oxide,aluminium oxide, zinc oxide or combinations thereof. More preferred areopacifying particles comprising zinc oxide, zirconium oxide, titaniumdioxide or a combination thereof as these materials have especially highrefractive index. Most preferred are opacifying particles comprisingtitanium dioxide. Preferably the composition comprises opacifyingparticles in an amount of from 0.001 to 10 wt %, more preferably 0.01 to7 wt %, more preferably still 0.02 to 5 wt % and most preferably 0.05 to2 wt %, wherein amount of particle active is in terms of weight of shellcomponent by weight of the composition.

Opacifying particles are preferably micronized. Preferably theopacifying particles have a primary particle size in the range of from20 to 2000 nm, and more preferably from 25 to 900 nm, and mostpreferably, from 30 to 400 nm, including all ranges subsumed therein.

The opacifying particles are typically separate from the particle active(i.e., the composition comprises particle active and additionallycomprises the opacifying particles). Owing to their greater opacifyingability, the opacifying particles are typically compounded in thecomposition at a lower level than the particle active. For example, thecomposition preferably comprises the particle active and opacifyingparticles in a weight ratio (particle active : opacifying particles) offrom 1000:1 to 1:1, more preferably 100:1 to 1.5:1, more preferablystill from 50:1 to 2:1 and most preferably from 20:1 to 3:1, whereinamount of particle active is in terms of weight of shell component.

The present inventors have also found that inclusion of yellow pigmentin the composition can help provide appearance benefits to skin. Inparticular it is found that the opacity afforded to skin by the particleactive and opacifying particles (when present) can occasionally appearin uneven “patches” even when the composition is applied evenly and thatthe presence of yellow pigment can ameliorate this effect. Thus in apreferred embodiment the composition comprises yellow pigment.

The yellow pigment is preferably present in an amount in the range of0.001 to 3 percent by weight of the composition, more preferably from0.01 to 2.5%, more preferably still from 0.05 to 2%, and most preferablyfrom 0.1 to 1.5%. The yellow pigment is preferably a metal oxide.Suitable metal oxides include titanium dioxide, iron oxide, or stannousoxide. Alternately the yellow pigment is of organic origin. Commerciallyavailable yellow pigments which may be used in the formulation includeBGYO-TTB2 (from Kobo Product Inc, USA), SI2 Yellow LLXLO (from DaitoKasei

Kogyo Company, Japan), Bronze 43737 (from Sudarshan Chemicals, India),Tatrazine Yellow (from Davarson, India), turmeric extract or a mixturethereof. Most preferred is iron oxide with the Colour Index ConstitutionNumber (C.I.) 77492.

The preferred metal oxide is yellow iron oxide. The iron oxide ispreferably suitably coated or encapsulated to minimize interactions withother ingredients of the composition. For example, when organicsunscreens are present in the formulation e.g.butylmethoxydibenzoylmethane sold as Parsol 1789 (Givaudan), theyinteract with iron oxide and produce an undesirable red colour. Tominimize such interaction, the metal oxide particles are preferablycoated with materials like mica and/or silicones (e.g. methyl hydrogenpolysiloxanes, more preferably silicones). An example of a coated yellowiron oxide is the aforementioned BGYO-TTB2 which has I.N.C.I Name: IronOxides (C.I. 77492) (And) Isopropyl Titanium Triisostearate (And)Triethoxysilylethyl Polydimethylsiloxyethyl Dimethicone.

In a preferred embodiment the composition may additionally oralternatively comprise red pigment, black pigment or a combinationthereof. More preferred is red pigment in combination with the yellowpigment, even more preferably the composition comprises yellow pigment,red pigment and black pigment. The total amount of pigment in thecomposition is preferably in the range 0.001 to 4 percent by weight ofthe composition, more preferably from 0.01 to 3%, more preferably stillfrom 0.05 to 2.5%, and most preferably from 0.1 to 2%.

Compositions of the present invention will also include a cosmeticallyacceptable carrier. The carrier comprises hydrophobic material, whereinthe hydrophobic material comprises less than 15% liquid oil by weight ofthe composition. The inventors have found that contact of the particleactive with large amounts of liquid oil can impair the optical benefitsafforded by the particle active. Preferably the hydrophobic materialcomprises less than 12% liquid oil by weight of the composition, morepreferably still less than 10%, even more preferably less than 8% andmost preferably from 0.01 to 5%.

In some embodiments the carrier will be (or at least comprise) a waterand oil emulsion, which in certain embodiments may be water-in-oilemulsion. Preferred emulsions, however, are the oil-in-water variety.Where the carrier is an emulsion, it is preferred that the particleactive is dispersed in the aqueous phase of the water and oil emulsionto minimize interaction of the particle active with any liquid oil inthe composition.

Regardless of the amount of liquid oil in the composition, thehydrophobic material may comprise non-liquid hydrophobic material. Inparticular the composition may contain non-liquid hydrophobic materialin an amount of from 0.01 to 80% by weight of the composition, morepreferably from 0.1 to 30%, more preferably still from 0.5 to 25% andmost preferably from 1 to 10%.

Preferred hydrophobic material for use in the present invention includesemollients such as fats, oils, fatty alcohols, fatty acids, soaps,silicone oils, synthetic esters and/or hydrocarbons. Many organicsunscreens are also hydrophobic materials and may be used alone or incombination with one or more of the foregoing emollients.

Silicones may be divided into the volatile and nonvolatile variety.Volatile silicone oils (if used) are preferably chosen from cyclic(cyclomethicone) or linear polydimethylsiloxanes containing from 3 to 9,preferably from 4 to 5, silicon atoms.

Nonvolatile silicones useful as an emollient material include polyalkylsiloxanes, polyalkylaryl siloxanes and polyether siloxane copolymers.The essentially nonvolatile polyalkyl siloxanes useful herein include,for example, polydimethyl siloxanes with viscosities of from about5×10⁻⁶ to 0.1 m²/s at 25° C. Among the preferred nonvolatile emollientsuseful in the present compositions are the polydimethyl siloxanes havingviscosities from about 1×10⁻⁸ to about 4×10⁻⁴ m²/s at 25° C.

Organopolysiloxane crosspolymers can be usefully employed.Representative of these materials are dimethicone/vinyl dimethiconecrosspolymers and dimethicone crosspolymers available from a variety ofsuppliers including Dow Corning (9040, 9041, 9045, 9506 and 9509),General Electric (SFE 839), Shin Etsu (KSG-15, 16 and 18[dimethicone/phenyl vinyl dimethicone crosspolymer]), and GrantIndustries (Gransil brand of materials), and lauryl dimethicone/vinyldimethicone crosspolymers supplied by Shin Etsu (e.g. KSG-31, KSG-32,KSG-41, KSG-42, KSG-43 and KSG-44).

Specific examples of non-silicone emollients include stearyl alcohol,glyceryl monoricinoleate, mink oil, cetyl alcohol, isopropylisostearate, stearic acid, isobutyl palmitate, isocetyl stearate, oleylalcohol, isopropyl laurate, hexyl laurate, decyl oleate, octadecan-2-ol,isocetyl alcohol, eicosanyl alcohol, behenyl alcohol, cetyl palmitate,silicone oils such as dimethylpolysiloxane, di-n-butyl sebacate,isopropyl myristate, isopropyl palmitate, isopropyl stearate, butylstearate, polyethylene glycol, triethylene glycol, lanolin, cocoabutter, corn oil, cotton seed oil, olive oil, palm kernel oil, rape seedoil, safflower seed oil, evening primrose oil, soybean oil, sunflowerseed oil, avocado oil, sesame seed oil, coconut oil, arachis oil, castoroil, acetylated lanolin alcohols, petroleum jelly, mineral oil, butylmyristate, isostearic acid, palmitic acid, isopropyl linoleate, lauryllactate, myristyl lactate, decyl oleate, myristyl myristate, andmixtures thereof.

Among the ester emollients are:

-   -   a) Alkenyl or alkyl esters of fatty acids having 10 to 20 carbon        atoms. Examples thereof include isoarachidyl neopentanoate,        isodecyl neopentanoate, isononyl isonanoate, cetyl ricinoleate,        oleyl myristate, oleyl stearate, and oleyl oleate;    -   b) Ether-esters such as fatty acid esters of ethoxylated fatty        alcohols;    -   c) Polyhydric alcohol esters. Butylene glycol, ethylene glycol        mono and di-fatty acid esters, diethylene glycol mono-and        di-fatty acid esters, polyethylene glycol (200-6000) mono- and        di-fatty acid esters, propylene glycol mono- and di-fatty acid        esters, polypropylene glycol 2000 monooleate, polypropylene        glycol 2000 monostearate, ethoxylated propylene glycol        monostearate, glyceryl mono- and di-fatty acid esters,        polyglycerol poly-fatty esters, ethoxylated glyceryl        mono-stearate, 1,3-butylene glycol monostearate, 1,3-butylene        glycol distearate, polyoxyethylene polyol fatty acid ester,        sorbitan fatty acid esters, and polyoxyethylene sorbitan fatty        acid esters are satisfactory polyhydric alcohol esters.        Particularly useful are pentaerythritol, trimethylolpropane and        neopentyl glycol esters of C₁-C₃₀ alcohols. Exemplative is        pentaerythrityl tetraethylhexanoate;    -   d) Wax esters such as beeswax, spermaceti wax and tribehenin        wax;    -   e) Sterols esters, of which cholesterol fatty acid esters are        examples thereof;    -   f) Sugar ester of fatty acids such as sucrose polybehenate and        sucrose polycottonseedate; or    -   g) mixtures of two or more of the foregoing (a) to (f).

Of particular use also are the C₁₂₋₁₅ alkyl benzoate esters sold underthe Finsolve brand.

Hydrocarbons which are suitable emollients include petrolatum, mineraloil, C₁₁-C₁₃ isoparaffins, polyalphaolefins, isohexadecane or a mixturethereof.

In a particularly preferred embodiment, the hydrophobic materialcomprises 1 to 25% fatty acid or 0.1 to 80% soap by weight of thecomposition. Mixtures of fatty acid and soap are also suitable e.g.vanishing cream base which gives a highly appreciated matty feel to theskin. C12 to C20 fatty acids are especially preferred for the presentinvention, more preferred being C14 to C18 fatty acids. The mostpreferred fatty acid is stearic acid, myristic acid or a mixturethereof. The fatty acid in the composition is more preferably present inan amount in the range of 5 to 20% by weight of the composition. Soapsin the hydrophobic material can include alkali metal salt of fattyacids, like sodium or potassium salts, most preferred being potassiumstearate. The soap in the hydrophobic material is generally present inan amount in the range of 0.1 to 10%, more preferably 0.5 to 3% byweight of the composition. Generally a vanishing cream base in cosmeticcompositions is prepared by taking a desired amount of total fattymatter and mixing with potassium hydroxide in desired amounts. The soapis usually formed in-situ during the mixing.

The carrier preferably comprises water. Amounts of water may, forexample, range from 1 to 99%, more preferably from 5 to 90%, even morepreferably from 35 to 80%, optimally between 40 and 70% by weight of thecosmetic composition.

The composition of the invention preferably comprises a skin lighteningagent. The skin lightening agent is preferably chosen from one or moreof a vitamin B3 compound or its derivative e.g. niacin, nicotinic acidor niacinamide or other well known skin lightening agents e.g.adapalene, aloe extract, ammonium lactate, anethole derivatives, appleextract, arbutin, azelaic acid, kojic acid, bamboo extract, bearberryextract, bletilla tuber, bupleurum falcatum extract, burnet extract,butyl hydroxy anisole, butyl hydroxy toluene, citrate esters,Chuanxiong, Dang-Gui, deoxyarbutin, 1,3-diphenyl propane derivatives,2,5-dihydroxybenzoic acid and its derivatives,2-(4-acetoxyphenyI)-1,3-dithane, 2-(4-hydroxyphenyI)-1,3-dithane,ellagic acid, escinol, estragole derivatives, Fadeout (Pentapharm),Fangfeng, fennel extract, ganoderma extract, gaoben, Gatuline Whitening(Gattlefosse), genistic acid and its derivatives, glabridin and itsderivatives, gluco pyranosyl-1-ascorbate, gluconic acid, glycolic acid,green tea extract, 4-hydroxy-5-methyl-3[2H]-furanone, hydroquinone,4-hydroxyanisole and its derivatives, 4-hydroxy benzoic acidderivatives, hydroxycaprylic acid, inositol ascorbate, lemon extract,linoleic acid, magnesium ascorbyl phosphate, Melawhite (Pentapharm),morus alba extract, mulberry root extract, 5-octanoyl salicylic acid,parsley extract, phellinus linteus extract, pyrogallol derivatives,2,4-resorcinol derivatives, 3,5-resorcinol derivatives, rose fruitextract, salicylic acid, Song-Yi extract, 3,4,5-trihydroxybenzylderivatives, tranexamic acid, vitamins like vitamin B6, vitamin B12,vitamin C, vitamin A, dicarboxylic acids, resorcinol derivatives,extracts from plants viz. rubia and symplocos, hydroxycarboxylic acidslike lactic acid and their salts e.g. sodium lactate, and mixturesthereof. Vitamin B3 compound or its derivative e.g. niacin, nicotinicacid or niacinamide are the more preferred skin lightening agent as perthe invention, most preferred being niacinamide. Niacinamide, when used,is preferably present in an amount in the range of 0.1 to 10%, morepreferably 0.2 to 5% by weight of the composition.

The composition preferably additionally comprises one or more organicsunscreens. A wide variety of organic sunscreen agents are suitable foruse in combination with the essential ingredients of this invention.Suitable UV-A/UV-B sunscreen agents include,2-hydroxy-4-methoxybenzophenone, octyldimethyl p-aminobenzoic acid,digalloyltrioleate, 2,2-dihydroxy-4-methoxybenzophenone,ethyl-4-(bis(hydroxypropyl))aminobenzoate,2-ethylhexyl-2-cyano-3,3-diphenylacrylate, 2-ethylhexylsalicylate,glyceryl p-aminobenzoate, 3,3,5-trimethylcyclohexylsalicylate,methylanthranilate, p-dimethyl-aminobenzoic acid or aminobenzoate,2-ethylhexyl-p-dimethyl-amino-benzoate, 2-phenylbenzimidazole-5-sulfonicacid, 2-(p-dimethylaminophenyI)-5-sulfonicbenzoxazoic acid,2-ethylhexyl-p-methoxycinnamate, butylmethoxydibenzoylmethane,2-hydroxy-4-methoxybenzophenone, octyldimethyl-p-aminobenzoic acid andmixtures thereof. The most suitable organic sunscreens are2-ethylhexyl-p-methoxycinnamate, butylmethoxydibenzoylmethane or amixture thereof.

A safe and effective amount of organic sunscreen may be used in thecompositions useful in the subject invention. The composition preferablycomprises from 0.1% to 10%, more preferably from 0.1% to 5%, of organicsunscreen agent.

Other materials which can be included in the cosmetically acceptablecarrier include solvents, humectants, thickeners and powders. Examplesof each of these types of material, which can be used singly or asmixtures, are as follows:

Solvents include ethyl alcohol, isopropanol, acetone, ethylene glycolmonoethyl ether, diethylene glycol monobutyl ether, diethylene glycolmonoethyl ether and mixtures thereof.

Humectants include those of the polyhydric alcohol-type. Typicalpolyhydric alcohols include polyalkylene glycols and more preferablyalkylene polyols and their derivatives, including propylene glycol,dipropylene glycol, polypropylene glycol, polyethylene glycol andderivatives thereof, sorbitol, hydroxypropyl sorbitol, hexylene glycol,1,3-butylene glycol, isoprene glycol, 1,2,6-hexanetriol, glycerol,ethoxylated glycerol, propoxylated glycerol and mixtures thereof. Theamount of humectant may range, for example, anywhere from 0.5 to 50%,more preferably between 1 and 15% by weight of the composition. Mostpreferred is glycerol (also known as glycerin). Amounts of glycerin mayrange, for example, from 0.5% to 50%, more preferably from 1 to 35%,optimally from 2 to 15% by weight of the composition.

A variety of thickening agents may be included in the compositions.Illustrative but not limiting are stearic acid, Acrylamide/SodiumAcryloyldimethyltaurate Copolymer (Aristoflex AVC), HydroxyethylAcrylate/Sodium Acryloyldimethyltaurate Copolymer, Aluminum StarchOctenyl Succinate, Polyacrylates (such as Carbomers including Carbopol®980, Carbopol® 1342, Pemulen TR-2® and the Ultrez® thickeners),Polysaccharides (including xanthan gum, guar gum, pectin, carageenan andsclerotium gums), celluloses (including carboxymethyl cellulose, ethylcellulose, hydroxyethyl cellulose and methyl hydroxymethyl cellulose),minerals (including talc, silica, alumina, mica and clays, the latterbeing represented by bentonites, hectorites and attapulgites), magnesiumaluminum silicate and mixtures thereof. Amounts of the thickeners mayrange, for example, from 0.05 to 10%, more preferably from 0.3 to 2% byweight of the composition.

Powders include chalk, talc, Fullers earth, kaolin, starch, gums,colloidal silica sodium polyacrylate, tetraalkyl and/or trialkyl arylammonium smectites, chemically modified magnesium aluminium silicate,organically modified montmorillonite clay, hydrated aluminium silicate,fumed silica, carboxyvinyl polymer, sodium carboxymethyl cellulose andethylene glycol monostearate.

The compositions of the present invention are not in a powdery form asit is desirable that the particle active is not broken on application toskin. Without wishing to be bound by theory, the present inventorsbelieve that the presence of the particle active in core-shell form onthe skin provides the advantageous optical effects of the invention. Thecompositions are thus in the form of a paste, gel, liquid or monolithicsolid (e.g. a soap bar). Preferred formats are creams or lotions.

The cosmetic composition of this invention is a composition suitable fortopical application to human skin, including leave-on and wash-offproducts. Preferably the term encompasses a fluid liquid, andparticularly a moisturizer rather than a make-up product. Most preferredare leave-on compositions.

Packaging for the composition of this invention can be a jar or tube aswell as any other format typically seen for cosmetic, cream, washing andlotion type products. The compositions may be applied topically andpreferably 1-4 milligrams of composition is applied per squarecentimeter of skin.

The following examples are provided to facilitate an understanding ofthe invention. The examples are not intended to limit the scope of theclaims.

EXAMPLES Example 1

This example demonstrates the manufacture of core-shell particles usefulfor the invention and wherein the shell is formed from sol-gelpolymerized inorganic polymer.

Materials

Styrene (St) was purchased from Sinopharm Chemical Reagent Co. (China)and purified by treating with 5 wt % aqueous NaOH to remove theinhibitor. An MTC [2-(methacryloyl)-ethyltrimethylammonium chloride] (80wt %) aqueous solution was supplied by SIGMA-ALDRICH, Co.(USA).2,2′-Azoisobutyronitrile (AIBN, 98%, Aldrich USA) was re-crystallizedfrom tetrahydrofuran (THF) before use. a,a′-azodiisobutyramidinedihydrochloride(AIBA), ploy(vinyl pyrrolidone) (PVP, K30, Mw=30 000),TEOS (triethylorthosilicate), absolute ethanol, and aqueous ammoniasolution (28 wt %) were purchased from Sinopharm Chemical ReagentCo.(China) and used as received. Deionized water was applied for allpolymerization and treatment processes.

Synthesis of PS Templates

Polystyrene particles with particle size above 1·m were synthesized bydispersion polymerization. In a typical procedure, positively charged PSparticles with a diameter of 1500 nm were synthesized as follows: 10.0 gof St, 3.0 g of PVP, 0.35 g of AIBN, 40.0 g of ethanol, 10.0 g of H₂Owere mixed in a 500 ml three-necked flask equipped with a mechanicalstirrer, thermometer with a temperature controller, an N₂ inlet, aGraham condenser, and a heating mantle. The mixing solution was firstdeoxygenated by bubbling nitrogen gas at room temperature for 30 min,and then heated to 70° C. with a stirring rate of 180 rpm for 1.5 h,followed by addition of a mixture of 10.0 g St, 40.0 g of ethanol and0.78 g of MTC.

Table 1 summarizes recipes for the synthesis of different sized PStemplate spheres (St 20 g, PVP 3.0 g, AIBN 0.35 g).

TABLE 1 H₂O (g) EtOH (g) EtOH(g)/H₂O (g) Particle size (nm) 15 75 1:51000 10 80 1:8 1500 7 83   1:11.8 1800

Synthesis of SiO₂ Hollow Spheres

In a typical run, 5.5 ml of ammonia was added to the above-obtaineddispersion and the mixture was stirred at 180 rpm for 5 min. 15 g ofTEOS was added quickly and the mixture was maintained at 50° C. foraround 1 h under constant stirring. The obtained spheres were separatedfrom the reaction solution by centrifuging at 10000 rpm for 7 min.PS/SiO₂ hybrid particles were dried at 80° C. overnight to yield driedpowders. The calcinations step used for removing PS core template wasperformed as the follows: the products were heated from room temperatureto 550° C. at a heating rate of 1° C./min in the air atmosphere and thenkept at 550° C. for another 2 h. Finally, the products were cooled downto room temperature in the air.

SEM images of the SiO₂ hollow spheres obtained with different diametersshowed that their diameters roughly equated with the diameters of the PStemplates (i.e., 1000 nm, 1500 nm or 1800 nm) and that the shell of eachparticle had a thickness of around 20 nm.

Example 2

Example formulations of two cosmetic compositions in the form ofvanishing creams according to the invention are given in Table 2.

TABLE 2 Ingredient (% w/w) Vanishing Cream 1 Vanishing Cream 2 StearicAcid 17 5 Myristic Acid — 5 Niacinamide 1.25 3 Glycerine 5 1 Propyleneglycol 10 — Neutralizing Agent (Base) 0.48 0.66 Carbomer — 0.2 TapiocaStarch — 0.7 Cetyl Alcohol 0.53 0.53 Dimethicone 0.5 0.563 Isopropylmyristate 1 — Methyl/propyl paraben 0.3 0.3 Parsol MCX (Ethylhexyl 0.751.25 Methoxycinnamate) Parsol 1789 (Butylmethoxy 0.4 0.4 DibenzoylMethane) Titanium Dioxide (80 nm)¹ 1 0.8 Titanium Dioxide (400 nm)² 2 —Pigment 1.29³ 0.015⁴ Core-Shell Particles 2 2 Minors⁵ 1.37 0.86 Water To100 To 100 ¹MT700Z = Titanium Dioxide (and) Stearic Acid (and) AluminiumHydroxide supplied by TAYCA - size in brackets is primary particle size²SA-TR-10 = Titanium Dioxide (and) Dimethylpolysiloxane supplied byMiyoshi Kasei Inc. - size in brackets is primary particle size. ³Mixtureof Yellow, Red and Black Pigments. ⁴Red Pigment. ⁵Minors includevitamins, perfumes, sequestrants, bacteriacides and other skin benefitagents.

The core-shell particles used in these formulations were the SiO₂ hollowspheres of Example 1.

Example 3

An example formulation of a cosmetic composition in the form of amoisturizer according to the invention is given in Table 3.

TABLE 3 Ingredient (% w/w) Moisturizer Stearic Acid 3 Niacinamide 3Glycerine 1 Neutralizing Agent (Base) 1.05 Carbomer 0.4 Cetyl Alcohol0.5 Mineral Oil 1.5 Glyceryl Monostearate 1.5 Dimethicone (200 cSt) 0.5Isopropyl Myristate 2 Methyl/Propyl Paraben 0.3 Parsol MCX (EthylhexylMethoxycinnamate) 1.25 Parsol 1789 (Butylmethoxy Dibenzoyl Methane) 0.4Titanium Dioxide (80 nm)¹ 0.6 Titanium Dioxide (400 nm)² 0.2 Pigment³0.068 Core-Shell Particles⁴ 1.5 Minors⁵ 1.211 Water To 100 ¹MT700Z.²SA-TR-10. ³Mixture of Yellow and Red Pigment. ⁴Prepared as inExample 1. ⁵Minors include vitamins, perfumes, sequestrants,bacteriacides and other skin benefit agents.

The liquid oil in this composition includes mineral oil, dimethicone,isopropyl myristate, ethylhexyl methoxycinnamate and phenoxyethanol. Thetotal amount of liquid oil is 5.7% by weight of the composition.

Example 4

This example demonstrates the effect of various particles on longlasting opacity in a moisturizer base.

Three samples were prepared using the moisturizer base described inExample 3 but with different amounts and/or types of opacifyingparticles and/or core-shell particles as shown in Table 4. These samplesdid not contain any red or yellow pigment.

TABLE 4 Ingredient (% w/w) Sample 1 Sample 2 Sample 3 Titanium Dioxide(80 nm) — 2.0 — Titanium Dioxide (400 nm) — — — SiO₂ Hollow Sphere¹ (1.5μm) — — 1.75 ¹Prepared as described in Example 1—amount is in terms ofSiO₂.

Opacity was measured using a Minolta™ CM2600D Spectrometer in SCE modeduring controlled drying (23° C. 45% RH) of applied film. For eachsample, a film was applied on a black/white draw-down card using a cubicfilm applicator of 75 microns.

Reflectance values of the film at various times after application weremeasured on both white and black backgrounds. The opacity was calculatedas the ratio of the reflectance on black/white background at thewavelength of 450 nm. Table 5 shows the change in opacity for eachsample film over 60 minutes (i.e., Opacity Change=opacity at 60minutes−opacity at 0 minutes).

TABLE 5 Sample Change in Opacity after 60 min 1 0.007 2 −0.077 3 0.195

These results demonstrate that the sample containing core-shellparticles (Sample 3) showed the ability to increase opacity with timeafter application.

Example 5

This example demonstrates the effect of opacifying particles andcore-shell particles on long lasting skin lightening in a moisturizerbase.

Two samples were prepared using the moisturizer base described inExample 3 but with different amounts of opacifying particles and/orcore-shell particles (1 micron SiO₂ spheres from Example 1) as shown inTable 6. These samples did not contain any red or yellow pigment.

TABLE 6 Ingredient (% w/w) Sample 1 Sample 2 Titanium Dioxide (80 nm) —0.6 Titanium Dioxide (400 nm) — — Core-Shell Particles¹ 2.0 2.0 ¹Amountis in terms of SiO₂.

Opacity was measured using a Minolta™ CM2600D Spectrometer in SCE modeduring controlled drying (23° C., 45% RH) of applied film. For eachsample, a film was applied on a black/white draw-down card using a cubicfilm applicator of 75 microns.

Reflectance values of the film at various times after application weremeasured on both white and black backgrounds. The opacity was calculatedas the ratio of the reflectance on black/white background at thewavelength of 450 nm. Table 7 shows the opacity for each sample filmover 60 minutes after application.

TABLE 7 Time (min) • Sample 1 • Sample 2 0 0.06 0.16 5 0.06 0.15 10 0.120.11 15 0.18 0.17 20 0.27 0.20 30 0.30 0.26 60 0.34 0.32

The data in Table 7 demonstrates that presence of opacifying particles(Sample 2) provides immediate opacity (i.e., opacity at 0 min) to thegreatest extent. However both samples showed an increase in opacity withtime. The use of core-shell particles in both samples resulted inopacity which remarkably increased during 60 minutes to a value highereven than that of the immediate lightness produced by the opacifyingparticles. However, the sample containing both opacifying and core-shellparticles (Sample 2) showed the best balance of both immediate andlong-lasting opacity.

Example 6

This example demonstrates the effect of liquid oil content on theability of core-shell particles to provide long lasting opacity.

Two moisturizer bases were used without pigments and opacifyingparticles. The first base is that used in the moisturizer of Example 3(“low liq. oil base”). The second base had a liquid oil content of over17 wt % (“high liq. oil base”). Core-shell particles (1.5 μm SiO₂particles of Example 1) were added to each base in an amount of 1.75%SiO₂ by weight of the final moisturizer composition.

Opacity was measured using a Minolta™ CM2600D Spectrometer in SCE modeduring controlled drying (23° C., 45% RH) of applied film. For eachsample, a film was applied on a black/white draw-down card using a cubicfilm applicator of 75 microns.

Reflectance values of the film at various times after application weremeasured on both white and black backgrounds. The opacity was calculatedas the ratio of the reflectance on black/white background at thewavelength of 450 nm. Table 8 shows the opacity for each sample filmover 60 minutes after application.

TABLE 8 Time (min) • Low liq. oil base High liq. Oil base 0 0.06 0.24 50.07 0.08 15 0.24 0.05 30 0.24 0.05 60 0.26 0.05

The data in table 8 demonstrates that the core-shell particles are ableto increase opacity after 60 minutes for the low liquid oil base. Incontrast in the high liquid oil base the hollow spheres were unable toprevent the opacity decreasing over 60 minutes after application.

Cryo-SEM images of the samples showed that, in contrast to thelow-liquid oil base, the core-shell particles in the high liquid oilbase appeared to be covered by and entrapped by oily material. Withoutwishing to be bound by theory the present inventors postulate that thiscovering may prevent or at least inhibit water from evaporating from theparticles as the film dries. Alternatively the coating of liquid oil mayreduce the refractive index contrast between the shell and thesurrounding medium such that scattering efficiency is reduced.

1. A cosmetic composition in the form of a paste, gel, liquid ormonolithic solid and comprising: (a) particle active, wherein theparticle active comprises: (i) water-insoluble shell componentcomprising inorganic material and having a refractive index (n_(s)) offrom 1.3 to 1.8; and (ii) core component comprising volatile liquid andhaving a refractive index (n_(c)) of at least 1.2, wherein the corecomponent comprises at least 75% water by weight of the core component;and (b) cosmetically acceptable carrier comprising hydrophobic material,wherein the hydrophobic material comprises less than 15% liquid oil byweight of the composition; and wherein the composition comprises 0.001to 3 wt % yellow pigment.
 2. The cosmetic composition as claimed inclaim 1 wherein the composition is a cream or lotion.
 3. The cosmeticcomposition as claimed in claim 1 wherein the inorganic material isinorganic polymer, preferably an inorganic polymer formed from silica,organically-modified silica, or a combination thereof.
 4. The cosmeticcomposition as claimed in claim 3 wherein the inorganic polymer isobtained by a sol-gel process.
 5. The cosmetic composition as claimed inclaim 1 wherein the particle active has a particle size (D) of at least200 nm, preferably at least 500 nm.
 6. The cosmetic composition asclaimed in claim 5 wherein the shell component has a thickness (L)obeying the following relationship (I):L≧150 nm−0.25×D   (I).
 7. The cosmetic composition as claimed in claim 1wherein the shell is permeable to water.
 8. The cosmetic composition asclaimed in claim 1 wherein the ratio of the refractive index of the coreto the refractive index of the shell (n_(c)/n_(s)) is from 0.7 to 1.2,preferably from 0.8 to 1.0.
 9. The cosmetic composition as claimed inclaim 1 wherein the composition additionally comprises opacifyingparticles having a refractive index of at least 1.7, preferably having arefractive index from 2.0 to 2.7.
 10. (canceled)
 11. The cosmeticcomposition as claimed in claim 1 wherein the hydrophobic materialcomprises liquid oil in an amount of from 0.01 to 10% by weight of thecomposition.
 12. The cosmetic composition as claimed in claim 1 whereinthe hydrophobic material comprises 1 to 25% fatty acid by weight of thecomposition, 0.1 to 80% soap by weight of the composition, or a mixturethereof.
 13. The cosmetic composition as claimed in claim 1 wherein thecarrier comprises non-liquid hydrophobic material in an amount of from0.5 to 30% by weight of the composition.
 14. A method for improving oneor more skin characteristics comprising the steps of: I. providing acomposition as claimed in claim 1 II. topically applying the compositionto skin; and III. allowing the volatile liquid to evaporate from theparticle active.
 15. (canceled)